The fifth in a series by staff writer Gerry Fraley reviewing the top 10 prospects in the Texas Rangers' organization. To qualify, a player must have his rookie status: fewer than 130 at-bats or 50 innings pitched in the majors and fewer than 45 days on an active roster before Sept. 1.

The combination of pennant-race trades in 2015-16 and graduations to the majors has created an imbalance in the Rangers' player-development system. The majority of the talent is concentrated at the lower levels of the organization. Of the players on this list, eight have not played above the High-A level.

General manager Jon Daniels recognized that when he sent right-hander Yu Darvish to the Los Angeles Dodgers for three prospects. The organization was "not where we want to be and where we'll be very quickly" at the upper levels, Daniels said.

The re-stocking continues this season. A look at the top 10 prospects in the organization going into spring training:

BRETT MARTIN

POSITION: Left-handed pitcher.

SIZE: 6-feet-4, 190 pounds.

OPENING DAY AGE: 22.

HOW ACQUIRED: Selected in the fourth round of the 2014 draft. Received a $475,000 signing bonus.

WORTH KNOWING: Martin deals with diabetes. He follows the examples of Dustin McGowan and Brandon Morrow, diabetics who pitched in the majors last season. Morrow appeared in all seven games of the World Series with the Los Angeles Dodgers and went to the Chicago Cubs in the offseason on a two-year deal worth $21 million.

AMATEUR BACKGROUND: Walters (Tenn.) State Community College produced two pitchers who went among the first four rounds of the 2014 draft: Martin and Tampa Bay right-hander Brent Honeywell. In their final season together, Martin and Honeywell were a combined 20-5 for a team that finished at 43-18.

NOTABLE: Martin has had an up-and-down professional career. There have been flashes of brilliance offset by hip and elbow injuries. Martin last season had difficulty repeating his delivery and also had trouble locating the curveball, his best pitch. He had a career-high walks-per-nine-innings rate of 3.7. Keeping the delivery intact has been a long-running concern for Martin. When right, he has dazzling stuff in addition to the curveball. He has added velocity, getting the fastball up to a consistent 94 mph with cutting movement.

NEXT STOP: Martin had minimal success in the High-A Carolina League last season, going 4-8 with a 4.70 ERA for 84 1/3 innings. The Rangers prefer that a player has success before being promoted. That could cause them to have Martin open the season at the same level.

PROJECTION: The curveball is in vogue again. That works in favor of Martin, if he can regain command of the pitch. Do that, and Martin could develop into a Drew Pomeranz-type starter.